This invention relates to a method of dressing a grinding wheel by a series of dressing steps during each of which dressing force is detected for controlling the number of steps of the operation.
In the example for conventional internal grinder shown in FIG. 1 a wheel table 2 having a grinding wheel speedle 1 thereon is movable in the axial direction of the spindle and an infeed table 4, having a work spindle (not shown in the drawing) which holds and drives a workpiece 3, is fed in a perpendicular direction to the wheel spindle 1. A dressing tool or dresser 5 is provided on one side of the infeeding table 4 and, after infeeding the infeeding table 4 by a predetermined amount and fixing the table there, the wheel table 2 is traversed to the dresser 5 by one or plural traverses.
It is usual in conventional grinding to determine an infeeding amount and the number of traverses of the dressing tool based on experience. But, it is very difficult to obtain best cutting edges on the wheel with this conventional dressing method, because the forming condition of cutting edges on the grinding wheel in a dressing process greatly affected by the kind (material) and the shape of the wheel, the shape of the diamond dresser and other parameters. Particularly in dressing a new-developed super hard grinding wheel (e.g. Borazon Grinding Wheel), a greater number of traverses than usual is required for dressing the wheel. Less than a required number of traverses is not enough for refreshing the abrasive gains of the wheel after a predetermined dressing infeed, while an excessive number of traverses brings loading on the wheel.
Both of the unsuitable numbers of traverses deteriorate grinding ability of the wheel. Further, in this particular manner of dressing, the most suitable number of traverses changes due to changes of the condition of the wheel to be dressed and to the wheel shape. Accordingly, it is preferable to select the number of traverses at every dressing operation according to the wheel condition or shape.
The inventor has, in an analysis of an experiment investigating dressing force and its relation to traverse number of the wheel table, discovered the phenomenon that dressing force decreases sharply at first but after that slowly decreases as traverse number increases as shown in FIG. 2 and the best cutting edge is formed on the grinding wheel in area A of the dressing force characteristic curve where the reducing ratio of dressing force suddenly changes to a small value.